Rimac's expertize in high-voltage battery technology and electric powertrains for use in high-end sports cars is attracting investment from automakers.

Porsche said it had raised its stake in Croatian sports-car maker Rimac to 15.5 percent.

In June 2018, Porsche took a 10 percent stake in Rimac, after the start-up company developed expertize in the area of high-voltage battery technology and electric powertrains for use in ultra high end sports cars.

In a news release on Friday, Lutz Meschke, Porsche's finance chief, said: "We have now increased our stake and intend to intensify our collaboration in the field of battery technology."

Rimac's EV expertize is attracting attention from automakers.

Hyundai has invested in a stake in Rimac and is developing an electric sports car in collaboration with the company.